Association between the Neutrophil-to-lymphocyte Ratio, and Platelet-to-lymphocyte Ratio and Rheumatoid Arthritis and their Correlations with the Disease Activity: A Meta-analysis

Objective. This study examined the relationship between neutrophil-to-lymphocyte ratio (NLR), platelet-to- lymphocyte ratio (PLR), mean platelet volume (MPV), and rheumatoid arthritis (RA), to establish a correlation among the NLR, PLR, and MPV and RA activity. Methods. Medline, Embase, and Cochrane were searched, and a meta-analysis was performed to compare the NLR, PLR, and MPV between RA patients and healthy controls. The correlation coefficients between NLR, PLR, and MPV and the Disease Activity Score 28 (DAS28) in the RA patients were examined. Results. Sixteen studies were included in this meta-analysis. NLR was significantly higher in the RA group (standardized mean difference [SMD], 0.800; 95% confidence interval [CI], 0.542 similar to 1.058; p<0.001). Stratification according to ethnicity revealed a significantly elevated NLR in the RA group in Asian and Turkish populations (SMD, 95% CI: 0.994, 0.418 similar to 1.519, p=0.001 and 0.695, 0.443 similar to 0.948, p<0.001, respectively). Subgroup analysis revealed a significantly high NLR in RA, independent of the data type and adjustment for age and/or sex. PLR was also significantly higher in the RA group (SMD, 0.708; 95% CI, 0.401 similar to 0.995; p<0.001), regardless of ethnicity, data type, and adjustment for age and/or sex. In addition, NLR and PLR were positively associated with the RA activity based on the DAS28 (correlation coefficient, 95% CI: 0.277, 0.190 similar to 0.359, p<0.001 and 0.318, 0.197 similar to 0.430, p<0.001, respectively). However, MPV showed no correlation with the RA activity (correlation coefficient, - 0.095; 95% CI, - 0.435 to 0.269; p=0.615). Conclusion. Meta-analysis showed that the NLR and PLR were significantly higher in the RA patients and positively but weakly correlated with the RA activity.